In the related art, a structure constituting a main wing of an aircraft is generally constituted of a metallic member such as an aluminum alloy. Accordingly, a metallic structure as described above has a secondary function of electrically grounding various electronic devices attached to a surface of the structure, that is, securing conduction with a reference potential point, as well as a function as the structural object.
However, from the point of view of weight reduction, strength reinforcement, or the like of a main wing, a principal structure of the main wing has recently been formed of a so-called composite material, for example, carbon-fiber-reinforced plastic (hereinafter abbreviated to as “CFRP”) (for example, see Patent Literature 1). A carbon-fiber-reinforced plastic structure (hereinafter abbreviated to “CFRP structure”) is configured by heating a carbon-fiber prepreg formed by laminating a plurality of sheets, each of which has a carbon fiber impregnated with a thermosetting resin, and hardening the thermosetting resins to integrate the plurality of sheets. Accordingly, in the above-described CFRP structure, a so-called resin layer is formed on a surface of the structure by the thermosetting resin exuded from the carbon fiber when the carbon-fiber prepreg is heated.